Inductance capacity tuner and circuit therefor



p 1950 R. M. BEUSMAN 2,521,963

INDUCTANCE CAPACITY TUNER AND CIRCUIT THEREFOR Filed Aug. 27, 1945 2Sheets-Sheet l 22?.2511731" @1751"? [Z fizz/5122522 ep 1950 R. M.BEUSMAN 2,521,963

INDUCTANCE CAPACITY TUNER AND CIRCUIT THEREFOR Filed Aug. 21', 1945 2Sheets-Sheet 2 7 ZZZ 51773.2"

. HaberTMBemmHzz Patented Sept. 12 1950 I NDU'GTAN CE CAPACITY TUNER ANDCIRCUIT THEREFOR Robert M. Beusman, Oak Park, Ill. Application August27, 1945, Serial No. 612,927

2 'Claims.

This invention relates to an inductance capacity tuner and circuittherefor, and more particularly to a means for varying the inductance ofa coil having current of very high frequency flowing therethrough.

Considerable diificulty has been experienced in the past in obtainingtuning of a circuit at very high frequency with apparatus which isrelatively low in cost. Ordinarily the factor of merit or in otherwords, the Q, for a, fixed coil and a variable condenser in a circuitcarrying current having a frequency of the order of magnitude of 50megacycles or higher, effectively is about 60 to 110. The factor ofmerit for permeability tuning is much higher, such, for example, as 200to 240 over a range of 50 to 70 megacycles, roughly. There are certaindisadvantages to permeability tuning, however, which are well-known tothose skilled in the art.

One of the principal features and objects of the present invention is toprovide a novel method and means for varying the inductance of a coil byvarying the magnetic shielding and short ing effect on the coil.

A further object of the present invention is to provide a novel methodand means for changing the inductance of a, coil carrying ultra highfrequency current which includes using one or more of the rotorcondenser plates of a variable condenser to vary the shielding of thecoil, and thereby vary the inductance thereof.

Another and further object of the present invention is to provide anovel method and means for forming a tuned circuit in ultra highfrequency apparatus, and for varying the tuning thereof.

Still a further object of the present invention is to provide a novelmethod and means for varying the inductance of a coil by providing aprogressive short-circuiting effect on the coil.

Still another and further object of thepresent invention is to provide anovel ultra high frequency radio circuit.

Still another and further objectof this invention is to provide avariable resonant circuit free from multi-ground returns, such as foundin variable air capacity tuning. Such variable capacitors normally havenumerous ground points which tend to produce high frequency eddy cur'-'rents in the condenser frame and chassis, resulting in losses. I

The novel features which I believe to be char.- acteristic of myinvention are set forth with par ticularity in the appended claims. Myinvention itself, however, both as to its method of operationand mannerof construction, together with further objects and advantages thereof,may best be understood by reference to the accompanying drawings, inwhich:

, Figure l is a diagrammatic end view of a gang condenser and inductancetuning element embodying the novel features and characteristics of I thepresent invention; I

Figure 2 is a diagrammatic front elevational view of the unit shown inFigure l of the draw- Figure 3 is a diagrammatic illustration of a radiocircuit including the novel inductance capacity tuner shown in Figures 1and 2;

Figure 4 is a diagrammatic end view similar to Figure 1 but showing amodified form of the present invention;

Figure 5 is a diagrammatic front elevational view of the embodiment ofthe invention shown in Figure 4 of the drawing;

Figure 6 is a diagrammatic view of a third embodiment of the presentinvention in which a shielding element reciprocates into and out ofshielding position with a plurality of inductance elements; and I 1Figure 7 is a diagrammatic bottom view of the embodiment of theinvention shown in Figure 6 of the. drawing.

Referring first to Figures 1 and 2 of the drawing, there is illustratedtherein a gang condenser I0 having three sections, ll, 12 and I3. Thisgang condenser I0 is of conventional design and each of its sections lI, I2 and I3 is provided with a plurality of stator plates I4 and aplurality of rotor plates 15 interposed between the stator plates. Therotor plates l5 are mounted in conventional manner on the rotor shaft [6and are arranged to bev moved from a position in which they are disposedsubstantially entirely between the stator. plates progressively to aposition where theyjare substantially entirely free of the stator plates[4; This provides a variable capacity effect in a conventional manner.

As is well known to those skilled in the art, the rotor plates may begiven any suitable shape but preferably are shaped in such a manner soas to provide proper tracking of the oscillator.

Three pancake inductance elements, l i, it and 1 9,are mounted oppositethe end rotor plates I5ofeach gang condenser section it, l2 and [3.

The inductance unit [9, asv seen in Figure l, is'

similar to the other inductance elements ll and I8 and may be said to begenerally spiral in shape." It has been found in practice that theparticular shape given to the inductance element w'ill'varyin accordancewith the particular shape of the rotor plate element 15, in order toprovide desirable tracking characteristics or to provide uniform changesin inductance with equal increment of change in the angular position ofthe rotor element [5.

The inductance element I8 has two terminal portions 20 and 2| which arearranged to be connected to other portions of the electrical circuit inwhich the tuning element is used.

Assume now that current is flowing through the inductance element I!) ata frequency of 30 megacycle or higher. This might, for example, becurrent in the frequency range of 88 to 108 megacycles, which is one ofthe higher frequency ranges in which this tuning element may be used togreat advantage. As the rotor plates [5 are rotated in acounterclockwise direction, as viewed in Figure 1 of the drawing, therotor plate I5 immediately adjacent the inductance element l9 graduallymoves into a position directly opposite the flat face of the coil. Thusas the rotor element l5'progressively moves opposite the coil 19, itintroduces a shorting effect on the coil which progressively increases.This causes the inductance of the coil to be reduced. It is alsoapparent that thi reduction in the inductance of the coil is due to ashielding eifect which the plate l5 has on the coil.

It is to be observed that here we are decreasing the inductance as eachplate'is moved into the field of the coil, while in permeability tuningthe inductance is increased as the powdered iron core member is movedinto the coil. In view of the fact that the inductance is decreased asyou move the plate into the field of the coil, it is possible to usealarger inductance coil than is possible with permeability tuning. Itwill furthermore be noted that the shielding comes into effect at a timewhen shielding becomes more and more desirable.

It will, of course, be apparent that the plate which is progressivelymoved into the field of the inductance coil doesno't have to be therotor plate, for any non-magnetic alloy or non-magnetic metal may beused, such, for example, as aluminum or copper. By combining theinductance element with a gang condenser, however, the rotor of the gangcondenser acts ina dual capacity; namely, it acts as a variable shieldfor tuning the inductance element or elements at ultra high frequencies,and it also acts in its conventional manner as a condenser for tuningcircuits at relatively low frequencies. An example of how the capacityinductance tuner may be used in a radio circuit is shownlin Figure 3 ofthe drawing.

The radio circuit diagrammatically illustrated in Figure 3 includestransmission line conductors 22 and 23 which connect an antenna (notshown) to either the ultra high frequency band antenna coil l! or to thebroadcast or low frequency "band antenna coil 24, depending upon thelocation of the band switch 25. When the band switch is in its upperposition as shown in Figure 3 of the drawing the broadcast antenna coil24 is shorted out to ground. When the switch 25 is in its lower positionthe broadcast antenna coil is in operating coimection in the circuit.While the ultra high frequency coil I! has not been cut out of thecircuit, it has substantially no effect.

since its inductance at broadcast or low frequency band frequencies isnegligible.

The broadcast antenna .coil 24 is arranged to be tuned by the variablecondenser H which is one section of the gang condenser l0 shown 'inFigures 1 and 2 of the drawing. M previously pointed out, the inductanceI! is tuned at ultra high frequencies by the adjacent end rotor plate ofthe variable condenser ll. Since it is the movement of the rotor ormovable element of the gang condenser whicheffects the tuning of theinductance element ll, at ultra high frequencies, these elements havebeen shown as mechanically related by means of the broken line The usualtrimmer condensers 21 and 28 are also provided for the coils 24 and I1respectively.

These two tuned circuits are connected to the input grid 29 of an R. F.amplifier tube or discharge device 30 by means of capacity coupling 3|.The resistance element 32 shown in the circuit of the input grid 29 ispart of the A. V. C. circuit as indicated. The electron discharge deviceorvacuum tube 30 may be of any conventional design and includes, inaddition to the input grid 29, an indirectly heated cathode 33 which isself-biased by a resistor-34. Filter condenser 35 shunts the biasingresistor 34 in the conventional manner. The indirectly heated cathode33is associated with a heater 36. The tube 30 also had a screen grid 31and ananode 38. The anode 38 is supplied with a positive bias from asource of uni-directional electric energy indicated as 13+ by the arrow39. More particularly, the B+ is connected through the low frequencyband coil 40 and on the ultra high fre quency band radio frequency coill8. A band switch 4|, mechanically associated with the switch '2 5, isarranged to short out the coil 40 in its upper position, therebyproviding ultra high frequency band reception. To render coil 4t effec:tive for operation in the low frequency band, the switch 4| is placed inits lower position. I A trimmer condenser 42 is connected in shunt withthe coil 40.. The coil 40 is further arranged to be selectively tuned bysection I2 of the gang condenser 10 shown in Figure 1 and 2 of thedrawing. Since it is the rotor plate of the sec-. tion 12 which effectstuning of the ultra high frequency coil 3, the variable condenser 12 andthe coil 1'8 have been indicated as being mechanig cally associated bymeans of shaft lli, as shown by the broken line 43. I .The screen grid31 of the. tube 30 receives its bias through a dropping resistor. Thisresistor 44 is provided with a radio frequency by-pass' condenser 45 asshown. Another radio frequency by-pass condenser 45 is also connected tothe movable element of the switch 4|. A trimmer condenser is provided inshunt with the coil l8.

Theorutput of the tube 30 as fed through "the tuned circuit is connectedthrough -a coupling condenser 48 to the input grid 49 of the multigridmixer tube 50. In addition to the inputgrid 49 the tube50 includes threeadditional grids El, 52 and Has well as a cathode 5 6, a'he'ater 55 andan anode 56.

The oscillator circuit includes a'low frequency band oscillating coil'51 which has connected thereacross the variable condenserjl3, whichissection l3 of the gang condenser h! shown in'Fig-,.

ures '1 and 2. It is also provided with a. trimmer condenser 58. Thecoil 15'! is tapped as at 59' and.

connected back through conductor .50 and the band switch 61 to thecathode 54 of the tube 50.

2&5215953 is connectedfromnthis -,taps-63,through a conductor 64 and theswitch 6| to. the cathode 54.

As previously discussed inconnection with the sections Hand I! ofthe'g'angcondenserlllfthe section" l3 is also mechanicallyassociatedwith the' tuning of the coil l9 and is therefore shown asbeingmechanically"associated by means of shaft [6 by the broken line 65. Theswitch 66, which is also part of the band switch, is arranged when inits upper position to short out the coil 51. Switch 66 when in its lowerposition connects the coil 5'l in its operating position in the circuit.It will further be noted that {the switch 6| selectively connectsthetapped portion 63 of the coil l9 or the tapped portion 59 of the coil51, depending upon whether the circuit is being used for the receptionof ultra high frequency waves or for the reception of waves in the lowfrequency band.

The grid elements 52 and 53 are connected together and through acondenser 61 to ground. They are also supplied with positive biasthrough a dropping resistor 81 from B+ energy source.

The anode 56 is connected through the conductor 68 to the ultra highfrequency band intermediate frequency coil 69 and then to the broadcastband intermediate frequency coil 10, the lower end of coil 70 beingconnected through a conductor H to the source of unidirectional electricenergy that supplies voltage for the anode 56 of tube 50. Coils 69 and10 are inductively coupled to coils l2 and 13, the latter being arrangedto be fed through the conductor 14 to the subsequent detector and audiofrequency ampliflcation stages. The coils 69, 10, 12 and 13 are providedin shunt circuit with condensers 15, I6, 11 and 18, respectively.Resonant circuits 69, I5 and l2, 11 are inductively coupled and aretuned, for example, to approximately 10.7 megacycles for the purpose ofreceiving signals in the ultra high frequency band. Resonant circuitsI0, 15 and 13, 18 are inductively coupled and are tuned, by way ofexample, to approximately 755 kilocycles for the purpose of receivingsignals in the low frequency band.

The 10.7 megacycle intermediate frequencies or the 455 kilocycleintermediate frequencies are amplified, detected, and the audiofrequency amplified and reproduced into audible frequencies inaccordance with general practice known to the art.

The audio frequency end of the radio circuit is not illustrated hereinfor the particular construction of the audio frequency end in no wayaffects the present invention.

The circuit which has been described above is arranged to receive radioenergy transmitted in the so-called broadcast band as well as ultra highfrequency energy, such, for example, as energy in the 88 to 108megacycle band.

A tap connection 88 on coil I! in Figure 3 may be used as an antennacoupling tap to 23 in place of the link or primary coil 89.

A second embodiment of the present invention is illustrated in Figures 4and 5 of the drawings. This particular form of the invention is similarto that shown in Figures 1 and 2 with the exception that the ultra highfrequency tuning coils l1 and I8 and I9 are mounted externally of theframe of the gang condenser Ill so that the coils are progressivelyshorted by adjacent rotor plates 15 when the rotor plates are moved outof the stator plates instead of between the plates which, as describedabove, occurs in the embodiment of Figures 1 and 2. It will be notedthat this is the Asecond difference in this ,embodi inventionv lies inthe fact that the coils ll, ltland 1.9 are positioned so that adjacentrotor platesv will passpn both sides of each coil ll, I8,,and l9.- Forthatreason the coils l1, l8 and is, are not positioned beyond the end ofthe lastrotor plate, but are positioned at an intermediate rplace alongthe rotor plateassembly. The short circuiting effect on the coils ll, l8and i9 is greater when so positioned, as, is;also the shielding effect.The coils are employed otherwise in the same manner asthat described inconnection withFi gures l, 2 and 3 of the drawings. i

A third embodiment of the present invention is illustrated in Figures 6and 7 of the drawings. More particularly, three ultra high frequencytuning coils l1, l8 and I9, are mounted on a base 80. Electrostaticshields 8i and 82 are disposed between adjacent coils, thereby to shieldeach coil from the other two. A plate 83 formed of conducting material,such, for example, as copper or aluminum, is mounted for reciprocalmovement into a position over the base and out to the position shown inFigures 6 and '7 of the drawings. This plate 83 is provided with threefinger portions 84, 85 and 86 which are arranged to progressively extendover the coils l1, l8 and I9 respectively as the member 83 is moved tothe right. This plate 83 provides a short circuiting effect on the coilsI1, l8 and I9 similar to the effect of shorting the secondary of atransformer. This, of course, brings about a reduction in the inductanceof the coils l1, l8 and Hi. It also provides a shielding effect whichprogressively reduces the inductance value of the coils as the member 83is moved into a position thereover. From the above description, it willice apparent that the third embodiment of the present invention issimilar to the first two embodiments of the invention with the principalexception that the short circuiting means is arranged for reciprocatingmovement rather than rotary movement.

While I have shown certain particular embodiments of my invention, itwill, of course, be understood that I do not wish to be limited thereto,since many modifications may be made and I, therefore, contemplate bythe appended claims to cover all such modifications as fall within thetrue spirit and scope of my invention.

I claim as my inventioni 1. In a radio frequency tuning device, thecombination of spaced parallel shield plates, a transverse shaftsupported thereby, a stator condenser plate, a pancake inductance coil,said stator plate and said coil supported in spaced relationshipparallel to and between said shield plates, a rotor condenser platesecured tosaid shaft for rotation therewith from a position remote fromto a position between and parallel to said stator plate and said coil,whereby the inductance of said coil is varied from a maximum to aminimum and the capacitance of said condenser plates is simultaneouslyvaried from a minimum to a maximum.

2. In a radio frequency tuning device, the, combination of spacedparallel shield plates, a transverse shaft supported thereby, aplurality of stator condenser plates and a pancake inductance coilmounted in spaced parallel relationship with and between said shieldplates, a plurality of rotor condenser plates secured to said shaft forEMT,

8 m 's'm me Pii'rw Number Number Name t eoidsnutn Feb. 2, 192:? i Pricer June 24, 1930 Book Feb. 14, 1939 Vain Billiard Feb. 8, 1944 Kar'pliiset a1 Jan. 23', 194i Sept. 1151945 FOREIGN PATENTS Country Date I 7Great Britain 1923 Germany Dec. '21-, 1918

